Relationship between Dissolved Oxygen and Corrosion Characterization of X80 Steel in Acidic Soil Simulated Solution

The relationship between dissolved oxygen (DO) and corrosion behavior of X80 steel in acidic soil simulated solution was studied by potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning Kelvin probe technique (SKP) and X-ray diffraction (XRD). Results showed that the presence of DO accelerated the cathodic process of corrosion for X80 steel in the acidic soil simulated solution. With the decrease of DO, 1/R-ct and i(corr) decreased gradually, the corrosion rate of X80 steel reduced. The corrosion of X80 steel was controlled by the ionization reaction when the content of DO in solution was bigger than 1.90 ppm. However, the diffusion of oxygen dominated the corrosion process of X80 steel in simulated solution with 0.85 ppm DO, as demonstrated by the presence of cathodic limiting diffusive current and Warburg impedance. Besides, DO could affect the formation and composition of the corrosion product formed on X80 steel. In O-2-saturated solution, a homogeneous and compact corrosion product layer,gamma-FeOOH and Fe3O4, formed on the surface of X80 steel. But the phase composition of corrosion product was gamma-FeOOH, Fe2O3 and a few FeCO3 when DO in solution was 0.85 ppm.